Node.js global objects and their use

In Node.js, a global object is an object that can be accessed from anywhere. These objects provide many useful functions and properties that can help us develop in the Node.js environment. This article will detail some common Node.js global objects and their use.

1. `global`Object

In Node.js, globalobjects are similar to objects in the browser environment window. It is a container for all global variables and functions and can be used anywhere. Using globalobjects, we can share data and methods between different files.

// 例子：在全局对象中定义变量和函数
global.name = 'Alice';
global.greet = function() {
    
    
  console.log('Hello, ' + global.name + '!');
};

// 在其他文件中使用全局对象
console.log(global.name);       // 输出: Alice
global.greet();                 // 输出: Hello, Alice!

While global variables can be accessed using globalthe object, it is best to avoid defining variables directly on the global object. The recommended practice is to put variables in the module's scope for better code organization.

2. `process`Object

processObject provides information and control about the current Node.js process. It is a global object and can be accessed directly. Through processthe object, we can handle command line parameters, obtain environment variables, control the behavior of the process, and so on.

Get command line arguments:

// 例子：获取命令行参数
console.log(process.argv);

Get environment variables:

// 例子：获取环境变量
console.log(process.env.PORT);

Behavior of the control process:

// 例子：终止进程
process.exit(1);

3. `console`Object

consoleThe object provides a set of methods for outputting information to the console. It is similar to the object in the browser environment consoleand can be used for debugging and logging.

output text:

// 例子：向控制台输出文本
console.log('Hello, World!');

Log error message:

// 例子：记录错误信息
console.error('Something went wrong!');

measure time:

// 例子：测量代码执行时间
console.time('MyOperation');
// 执行一些操作
console.timeEnd('MyOperation');

4. `setTimeout`And `setInterval`function

setTimeoutThe and setIntervalfunctions are timer functions provided by the global object. They can be used to execute code after a specified time interval.

setTimeoutThe function is used to execute once after a specified time:

// 例子：延迟执行代码
setTimeout(function() {
    
    
    console.log('Delayed code execution');
}, 2000); // 2秒后执行

setIntervalFunctions are used to repeatedly execute code at specified intervals:

// 例子：重复执行代码
var interval = setInterval(function() {
    
    
    console.log('Repeated code execution');
}, 1000); // 每秒执行一次

// 清除定时器
setTimeout(function() {
    
    
    clearInterval(interval);
}, 5000); // 5秒后停止执行

5. Other common global objects

In addition to the global objects introduced above, there are some other common global objects that can be used in Node.js.

BufferObject: Used to handle binary data.
requireFunction: Used to load modules.
moduleObject: Represents the current module itself.
__filenameand __dirnamevariables: represent the path of the current file and the path of the directory where the current file is located, respectively.

in conclusion

This article details some common global objects and their use in Node.js. The global object provides many useful functions and properties that can help us develop in the Node.js environment. You can flexibly use these global objects according to your needs to write Node.js applications more efficiently.

When using global objects, it is recommended to choose the appropriate method according to the needs. Try to avoid defining variables directly on the global object, instead put variables in the appropriate module scope. This can better organize the code, improve the readability and maintainability of the code.

Hope this article helps you understand and use Node.js global objects. Using global objects, you can better grasp the development capabilities of Node.js and build more powerful and efficient applications.